The goal is to investigate the relationship between proteins associated with secondary amyloidosis and inflammatory and neoplastic diseases. Specifically, studies are planned to determine if serum amyloid A (SAA) is synthesized by neoplastic cells or is a factor synthesized as a reaction to a neoplasm. SAA is a serum alpha globulin known to be present in increased amounts in inflammatory diseases as well as in cancer. It has previously been shown to suppress the in vitro formation of antibody by CBA/J murine splenic lymphocytes. Studies on 50 patients with carcinoma of the lung have shown significant suppression of peripheral blood lymphocytes (PBL) mitogenic response to phytohemagglutinin (PHA) and Con A. In addition, serum levels of SAA were significantly elevated without correlation with tumor cell type. There was a lack of correlation between SAA level and mitogenic response of PBL to both PHA and Con A. In addition, no correlation was found between SAA levels at the time of diagnosis and survival. Studies on the in vitro effects of SAA in the murine system have shown that inhibition of the T-dependent antigen response of splenic lymphocytes can be restored with combinations of normal T cells and macrophages. This suggests that SAA may cause immunosuppression by affecting T cellmacrophage interaction.